Question

Воспользуйся формулой
(1+c+d)^2=(1+c)^2+2*(1+c)*d+d^2=
Раскрой скобки

Answer 1

${(1 + c + d)}^{2} = {( 1 + c)}^{2} + 2 \times (1 + c) \times d + {d}^{2} = 1 + 2c + {c}^{2} + 2d + 2cd + {d}^{2}$